What’s going on w my cat?

Hi! (I have been to the vet and am going back in about a week but vet is not really getting to the bottom of anything so hoping for insight from people who have seen their cat behave similarly!)

My 15 year old cat has started acting funky in the last couple weeks. He is biting lots of things somewhat gently, including me. While I’m sleeping, he will come over for pats and rub his face into my hand then slowly chomp on my hand and arm. Not an angry bite, but also stronger than his usual ‘hi I love you pay attention to me’ nibbles. Then I saw him doing this today. He gets annual dental cleanings and a year ago had some teeth pulled because of dental resorption which the vet couldn’t see until he was already sedated. I had that dental cleaning done on instinct because he was making funky faces while eating his dry food. Even though the vet looked at his mouth and said his teeth were looking mostly ok, I decided to do the cleaning then because I knew anesthesia as he got older would be harder.

So back to present - he’s eating just fine. I brush his teeth and get a normal amount of protest from him but he allows it and it doesn’t seem to hurt him. But, he’s also doing this weird biting me and things behavior he’s not really done in the 9 years I’ve had him.

The vet saw him for senior bloodwork and a checkup and we’re waiting for bloodwork results but she isn’t seeing anything notable on checkup. I’m out of town for work right now but taking him back to the vet as soon as I get home for a second opinion. In the meantime - has anyone had this behavior from their cats before or have any insight on what I’m dealing with?

He was also overweight for quite a while and after years of vet-guided weight loss he’s finally at a healthy weight - but he looks skinny to me. Am I just used to him being a little thick? I know he’s 15 and his age is just beginning to show a little, but it seems like his mobility isn’t quite what it used to be. He plays and runs and jumps while playing but he sleeps a lot more now than he used to and when he isn’t playing he is just a bit… stiff. I got him a heated bed for his gotcha day a few weeks ago which he seems to love.

If it’s just age, what can I do to make things easier on him? He is my first cat.